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Immunization against a merozoite sheddase promotes multiple invasion of red blood cells and attenuates Plasmodium infection in mice.

Smith RC, Colón-López DD, Bosch J - Malar. J. (2014)

Bottom Line: Subtilisin-like protease 2 (SUB2) is a conserved serine protease utilized by Plasmodium parasites as a surface sheddase required for successful merozoite invasion of host red blood cells and has been implicated in ookinete invasion of the mosquito midgut.Moreover, SUB2 immunization results in an increase in the number of multiply invaded red blood cells, suggesting that SUB2 antibodies interfere with merozoite invasion.Passive immunization experiments imply that SUB2 may not have a major role in ookinete invasion, but this requires further investigation.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry and Molecular Biology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA. jbosch@jhu.edu.

ABSTRACT

Background: Subtilisin-like protease 2 (SUB2) is a conserved serine protease utilized by Plasmodium parasites as a surface sheddase required for successful merozoite invasion of host red blood cells and has been implicated in ookinete invasion of the mosquito midgut. To determine if SUB2 is a suitable vaccine target to interfere with malaria parasite development, the effects of SUB2-immunization on the Plasmodium life cycle were examined in its vertebrate and invertebrate hosts.

Methods: Swiss Webster mice were immunized with SUB2 peptides conjugated to Keyhole limpet hemocyanin (KLH) or KLH alone, and then challenged with Plasmodium berghei. To determine the effects of immunization on parasite development, infected mice were evaluated by blood film and Giemsa staining. In addition, collected immune sera were used to perform passive immunization experiments in non-immunized, P. berghei-infected mice to determine the potential role of SUB2 in parasite development in the mosquito.

Results: Following P. berghei challenge, SUB2-immunized mice develop a lower parasitaemia and show improved survival when compared to control immunized mice. Moreover, SUB2 immunization results in an increase in the number of multiply invaded red blood cells, suggesting that SUB2 antibodies interfere with merozoite invasion. Passive immunization experiments imply that SUB2 may not have a major role in ookinete invasion, but this requires further investigation.

Conclusion: By interfering with red blood cell invasion, immunization against SUB2 limits malaria parasite development and confers protection from severe malaria. Together, these results provide proof-of-principle evidence for future investigation into the use of SUB2 as a vaccine or drug target to interrupt parasite development in more relevant human malaria models.

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SUB2 immunization reduces the intensity ofPlasmodium bergheiinfection and increases mouse survival. The parasitaemia of KLH- or SUB2-immunized mice was determined over the period of ten days after infection with P. berghei parasites (A). Each point represents the mean parasitaemia (n = 9) with error bars displaying standard errors of the mean and the asterisk denoting significance (P = 0.0042). The scatter plot displays the parasitaemia at day 10, with each point representing the parasitaemia of individual KLH- or SUB2-immunized mice (B). The red bar represents the median of each experiment with the asterisk denoting significance (P < 0.05). The survival of KLH- and SUB2-immunized mice was monitored over the course of forty days following P. berghei challenge (C). The number of surviving mice for each treatment over the duration of the experiment is displayed as a percentage of the total number of infected mice at a given time point. Statistical differences are marked by an asterisk (P = 0.0082).
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Fig3: SUB2 immunization reduces the intensity ofPlasmodium bergheiinfection and increases mouse survival. The parasitaemia of KLH- or SUB2-immunized mice was determined over the period of ten days after infection with P. berghei parasites (A). Each point represents the mean parasitaemia (n = 9) with error bars displaying standard errors of the mean and the asterisk denoting significance (P = 0.0042). The scatter plot displays the parasitaemia at day 10, with each point representing the parasitaemia of individual KLH- or SUB2-immunized mice (B). The red bar represents the median of each experiment with the asterisk denoting significance (P < 0.05). The survival of KLH- and SUB2-immunized mice was monitored over the course of forty days following P. berghei challenge (C). The number of surviving mice for each treatment over the duration of the experiment is displayed as a percentage of the total number of infected mice at a given time point. Statistical differences are marked by an asterisk (P = 0.0082).

Mentions: To monitor the effects of immunization on parasite development, KLH- and SUB2-immunized (IFA or CFA) mice were challenged with ~2×102P. berghei parasites by intravenous injection and the parasitaemia was monitored over the period of ten days. Blood stage infections were detected in 17 of 18 mice, and little variation was seen between mice immunized with the IFA or CFA immunization protocols (Table 1). As a result, both immunization experiments were pooled for analysis and are summarized in Table 1. Compared to control KLH-immunized mice, SUB2-immunized mice showed a slight, but not significant delay in the pre-patency of infection (Table 1). However, when the parasitaemia was monitored over the period of ten days (Additional file 1), asexual growth was significantly reduced and in some mice completely attenuated following SUB2-immunization (Figure 3A).Table 1


Immunization against a merozoite sheddase promotes multiple invasion of red blood cells and attenuates Plasmodium infection in mice.

Smith RC, Colón-López DD, Bosch J - Malar. J. (2014)

SUB2 immunization reduces the intensity ofPlasmodium bergheiinfection and increases mouse survival. The parasitaemia of KLH- or SUB2-immunized mice was determined over the period of ten days after infection with P. berghei parasites (A). Each point represents the mean parasitaemia (n = 9) with error bars displaying standard errors of the mean and the asterisk denoting significance (P = 0.0042). The scatter plot displays the parasitaemia at day 10, with each point representing the parasitaemia of individual KLH- or SUB2-immunized mice (B). The red bar represents the median of each experiment with the asterisk denoting significance (P < 0.05). The survival of KLH- and SUB2-immunized mice was monitored over the course of forty days following P. berghei challenge (C). The number of surviving mice for each treatment over the duration of the experiment is displayed as a percentage of the total number of infected mice at a given time point. Statistical differences are marked by an asterisk (P = 0.0082).
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4248431&req=5

Fig3: SUB2 immunization reduces the intensity ofPlasmodium bergheiinfection and increases mouse survival. The parasitaemia of KLH- or SUB2-immunized mice was determined over the period of ten days after infection with P. berghei parasites (A). Each point represents the mean parasitaemia (n = 9) with error bars displaying standard errors of the mean and the asterisk denoting significance (P = 0.0042). The scatter plot displays the parasitaemia at day 10, with each point representing the parasitaemia of individual KLH- or SUB2-immunized mice (B). The red bar represents the median of each experiment with the asterisk denoting significance (P < 0.05). The survival of KLH- and SUB2-immunized mice was monitored over the course of forty days following P. berghei challenge (C). The number of surviving mice for each treatment over the duration of the experiment is displayed as a percentage of the total number of infected mice at a given time point. Statistical differences are marked by an asterisk (P = 0.0082).
Mentions: To monitor the effects of immunization on parasite development, KLH- and SUB2-immunized (IFA or CFA) mice were challenged with ~2×102P. berghei parasites by intravenous injection and the parasitaemia was monitored over the period of ten days. Blood stage infections were detected in 17 of 18 mice, and little variation was seen between mice immunized with the IFA or CFA immunization protocols (Table 1). As a result, both immunization experiments were pooled for analysis and are summarized in Table 1. Compared to control KLH-immunized mice, SUB2-immunized mice showed a slight, but not significant delay in the pre-patency of infection (Table 1). However, when the parasitaemia was monitored over the period of ten days (Additional file 1), asexual growth was significantly reduced and in some mice completely attenuated following SUB2-immunization (Figure 3A).Table 1

Bottom Line: Subtilisin-like protease 2 (SUB2) is a conserved serine protease utilized by Plasmodium parasites as a surface sheddase required for successful merozoite invasion of host red blood cells and has been implicated in ookinete invasion of the mosquito midgut.Moreover, SUB2 immunization results in an increase in the number of multiply invaded red blood cells, suggesting that SUB2 antibodies interfere with merozoite invasion.Passive immunization experiments imply that SUB2 may not have a major role in ookinete invasion, but this requires further investigation.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry and Molecular Biology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA. jbosch@jhu.edu.

ABSTRACT

Background: Subtilisin-like protease 2 (SUB2) is a conserved serine protease utilized by Plasmodium parasites as a surface sheddase required for successful merozoite invasion of host red blood cells and has been implicated in ookinete invasion of the mosquito midgut. To determine if SUB2 is a suitable vaccine target to interfere with malaria parasite development, the effects of SUB2-immunization on the Plasmodium life cycle were examined in its vertebrate and invertebrate hosts.

Methods: Swiss Webster mice were immunized with SUB2 peptides conjugated to Keyhole limpet hemocyanin (KLH) or KLH alone, and then challenged with Plasmodium berghei. To determine the effects of immunization on parasite development, infected mice were evaluated by blood film and Giemsa staining. In addition, collected immune sera were used to perform passive immunization experiments in non-immunized, P. berghei-infected mice to determine the potential role of SUB2 in parasite development in the mosquito.

Results: Following P. berghei challenge, SUB2-immunized mice develop a lower parasitaemia and show improved survival when compared to control immunized mice. Moreover, SUB2 immunization results in an increase in the number of multiply invaded red blood cells, suggesting that SUB2 antibodies interfere with merozoite invasion. Passive immunization experiments imply that SUB2 may not have a major role in ookinete invasion, but this requires further investigation.

Conclusion: By interfering with red blood cell invasion, immunization against SUB2 limits malaria parasite development and confers protection from severe malaria. Together, these results provide proof-of-principle evidence for future investigation into the use of SUB2 as a vaccine or drug target to interrupt parasite development in more relevant human malaria models.

Show MeSH
Related in: MedlinePlus